Treatment of fluid flows



Oct. 2, 1962 F. D. CARTER 3,056,500

TREATMENT OF FLUID FLOWS Filed April 4, 1960 INVENTOR Fesbekucx D. CamsaATTORNEY rates Patent @fflce 3,056,500 Patented Oct. 2, 1962 3,056,560TREATMENT F FLUID FLQWS: Frederick Denis Carter, 2 Brooklyn Gardens,Cheltenham, Engiand Filed Apr. 4, 1961), Ser. No. 19,775 8 Claims. (Cl.21013t This invention relates to treatment processes incorporated influid flows, and is particularly concerned with a means and method foreffecting such treatment processes.

In many processes a specific treatment of a fluid flow, for examplefiltration to remove an unwanted component, is of secondary importanceto the maintenance of the fluid flow. In some cases it is essential fromthe point of view of safety that the flow should be maintained even atthe expense of temporary cessation of the treatment.

Hitherto when fluid flow treatment means, for example a filter section,has been introduced into a pipeline used for a process in which themaintenance of flow is of importance, normally either two sections ofsuch means have been connected in valved parallel branches of thepipeline or one section has been connected in parallel with a valvedby-pass. In the former case, when blockage of the section in use occurs,it is isolated for clearing and the parallel section brought into use,whilst in the latter case the section can be isolated and the by-passbrought into use. Even more complicated arrangements have been used, forexample the provision of two or more Sections in parallel with a valveby-pass.

In all such arrangements partial or complete blockage of the section inuse affects the process flow and the blockage may not be noticed andcorrected for some time. In particular, where the section has toincorporate fluid displacement means to overcome the resistance to flowpresented by the treatment means, the action of the fluid displacementmeans, as they are directly in line with the process flow, affects thepressure conditions of the flow and if the fluid displacement meansbreaks down the process flow is obstructed. As the section handles themain flow of a process the continuity of which is essential, eitherblockage or breakdown of the fluid displacement means can represent adangerous hazard as a no-flow condition can arise. It must be borne inmind that the process flow itself may take any one of many forms, andmay for example result from chemical action alone or be produced orassisted by means of a pump, fan, ejector or the like. It may becontinuous or batchwise, and it may be straight-through or recycling viaa reservoir.

The treatment process may involve one or more of a wide range of unitoperations, such as filtration, clarification, absorption, softening andlike component separation processes. Where the treatment involves or caninvolve a significant resistance to flow, the treatment process mayrequire the use of a treatment section incorporating its own prime moverand fluid displacement means, and defects in the section can cause anundue pressure rise in the process flow before the treatment section oran undue pressure drop or suction after it, either of which conditionsmay adversely affect the main process or even introduce a hazard.

The main object of the invention is to provide a fluid flow treatmentmeans and method with which, in the event of complete or partialblockage of the treatment section, continuance of the flow normallytreated is assured. A further object is to provide such a means andmethod with which such complete or partial blockage producessubstantially no additional impedance to full flow or additionalresistance opposing the flow.

According to the invention means for the treatment of fluid flowscomprises a pump or other fluid displacement means connected in serieswith treatment apparatus, the pump having a rate of fluid displacement,against the normal total working resistance of the treatment section,greater than the normal maximum rate of said fluid flow, and a normallyopen by-pass connected in parallel with the pump and apparatus.

In normal operation the volume of fluid displaced by the fluiddisplacement means in excess of said fluid flow is recirculated aroundthe by-pass, the flow of this excess through the by-pass being in theopposite direction to that which applies when a flow is being permittedto pass through a valve by-pass as in the prior art. Thus, the treatmentmeans automatically adjusts itself to compensate for any partial orcomplete blockage of the apparatus or breakdown of the pump, and in theevent of complete blockage the full fluid flow passes through theby-pass in the normal direction of the prior art but without thenecessity for opening a valve. Thus a hazardous no-flow condition cannotoccur, even momentarily or dur' ing the gradual transition during ablockage build-up when the flow through the by-pass automaticallyreduces, reverses and then increases, finally reaching the full flowcondition at the complete blockage stage.

In addition, when treatment means according to the invention areutilised in a treatment process this and the main process are pressureindependent. Any resistance to flow produced by the treatment apparatusis absorbed by the power and capacity of the pump during normaloperation and any increase in resistance to flow arising during abuild-up of the blockage in the apparatus is accommodated by thepresence of the by-pass, so that in neither case has the resistance toflow of the treatment section any material influence on the pressureconditions in the main process flow.

Shut-off valves may be provided to isolate the pump and treatmentapparatus for clearing in the event of blockage or breakdown, theoperation of these valves leaving the by-pass open. The by-pass itselfis preferably valveless so that there is no chance of it beinginadvertently left closed.

The treatment section may be duplicated in parallel so that in the eventof blockage of the section in use the alternative parallel section maybe brought into service. These sections may share a common by-pass alongwhich the full flow occurs in the interval before and during change overto the alternative section.

Preferably the by-pass is of die cross-section so that it provides a lowor negligible impedance to flow therethrough and cannot conceivablyblock up, and it may conveniently be a short length of pipe of the sameor preferably greater diameter than the pipe carrying said fluid flow tothe treatment means. However, the valveless by-pass must not generallybe shorter than approximately three times its diameter, as otherwise acertain amount of untreated fluid may short circuit the treatmentsection during normal operation of the treatment means.

The invention also includes a method of treating a fluid flow whichcomprises passing said fluid through a treatment zone at a rate greaterthan said fluid flow thereby to effect the treatment, and recirculatingthe excess along a substantially unrestricted flow path.

The invention will now be described with reference to the accompanyingdrawings which illustrate, by way of example, means for the treatment offluid flows in accordance with the invention, and in which:

FIGURE 1 is a flow diagram of the means, and

FIGURE 2 is a similar diagram showing the means incorporated in a plant,for example an oil-gas plant.

The treatment means comprise an inlet pipeline 1 and an outlet pipeline2 connected in series with a pipeline 3 in which is connected a pump orother fluid displacement means and treatment apparatus 6. The latter is,for example, a filter. A valveless by-pass 4 in parallel with thepipeline 3 interconnects the inlet and outlet pipelines 1 and 2, and thepipeline 3 is valved at 7 to cut off the flow through the pump 5 andapparatus 6 for maintenance purposes.

The pump 5 has a normal rate of fluid displacement, against the normaltotal working resistance of the treatment apparatus 6, greater than thenormal maximum rate of fluid flow through the pipelines 1 and 2. Thedirection of flow through the two latter pipelines is as shownrespectively by the arrows A and D, and the flow through the pipeline 3assisted by the pump 5 is in the direction of the arrow C; thus, theexcess volume of fluid displaced by the pump 5 is recirculated aroundthe bypass 4 in the opposite direction, i.e. in the direction of thearrow B. As a result, the treatment means automatically adjusts itselfto compensate for any partial or complete blockage of the apparatus 6 orbreakdown of the pump 5, and in the event of complete blockage the fullfluid flow passes through the by-pass 4 in the conventional direction,i.e. against the arrow B, without the necessity for opening any valvesin the by-pass 4.

The system is thus self-compensating and a hazardous no-flow conditioncannot occur, even momentarily, and the treatment process and the mainprocess with which it is associated are pressure independent. Anyresistance to flow produced by the apparatus 6 is absorbed by the powerand capacity of the pump 5 during normal operation and any increase inresistance to flow arising during a build-up of blockage in theapparatus 6 is accommodated by the presence of the permanently openby-pass 4.

The means of FIGURE 1 can be incorporated in a plant as shown in FIGURE2, in which a section of the plant producing the fluid flow to betreated is shown at 8 and a further section of the plant to which thetreated flow is supplied is shown at 9.

One particular application of the invention is in the cleaning ofcarbon-laden gas produced by an oil-gas plant, corresponding to thesection 8, before the gas enters a gas holder, corresponding to thesection 9, for storage. In this case the treatment means comprise a fan5 and filter 6 and as the gas flow is discontinuous, being interruptedbetween spaced make periods, the flow passed through the filter by thefan 5 in the direction of the arrow C is arranged to be greater than themaximum gas flow during a make period. During the make periods thetreated excess is recirculated back along the by-pass 4 in the directionof the arrow B and in parallel with the fan 5 and filter 6, and in theintervening periods the complete volume displaced by the fan 5recirc-ulates through the by-pass 4 and pipeline 3 containing the filter6.

In the event of breakdown of the fan 5, or blockage of the filter 6, thecomplete gas flow during the make periods passes substantiallyunrestricted in the opposite direction to the arrow B along the by-pass4. With an application such as this, the cleaning of the gas, thoughhighly desirable, is of secondary importance to the maintenance of gasflow. Any major restriction of the latter would result in thedevelopment of a dangerous overpressure in the gas plant 8.

Some examples of treatment processes with which the invention may veryconveniently be used, and in which it is essential that partial orcomplete discontinuance of the main process flow to which they aresubsidiary should not be allowed to occur, are: oil filtrationassociated with an engine lubrication system; filtration andhumidification associated with an air conditioning system; and softeningand clarification associated with a water supply system. Furtherexamples, in which the subsidiary processes are of such nature thatblockage thereof is rather unlikely, but where the invention may beemployed where it is desired to guard against the danger which wouldresult if such blockage did occur, are: the removal of S0 associatedwith an ore smelting process; noxious gas removal associated with suchprocesses as nitration and chlorination; and the removal of fly ashassociated with a steam raising process.

I claim:

1. Apparatus for the treatment of a fluid flow comprising a fluid inlet;a fluid outlet; a fluid treatment section connected between the inletand the outlet and comprising fluid displacement means and fluidtreatment means having a normal resistance to fluid flow therethroughbut being liable to exhibit an increased resistance to reduce or inhibitfluid flow therethrough, the treatment means being connected in serieswith the fluid displacement means; and a by-pass connected between theinlet and the outlet in parallel with the treatment section, the by-passbeing permanently open during operation of the apparatus; wherein thefluid displacement means has a rate of fluid displacement greater thanthe rate of fluid flow through the inlet under normal operatingconditions of the apparatus so that under said conditions the fluiddisplacement means draws fluid from both the by-pass and the inlet andwherein fluid passes from the inlet to the outlet along the by-pass uponan increase of said resistance above a predetermined value.

2. Treatment means according to claim 1, wherein the by-pass is of Widecross-section so that it provides a low or negligible impedance to flowtherethrough.

3. Treatment means according to claim 2, wherein the by-pass is a shortlength of pipe of the same or greater diameter than a pipe carrying saidfluid flow to the treat ment means.

4. Treatment means according to claim 3, wherein the pipe forming saidby-pass is not shorter than approximately three times its diameter.

5. Treatment means according to claim 1, wherein said treatmentapparatus comprises a filter.

6. Apparatus for the treatment of a fluid flow comprising a fluid inlet;a fluid outlet; a fluid treatment section connected between the inletand the outlet and comprising fluid displacement means and fluidtreatment means having a normal resistance to fluid flow therethroughbut being liable to exhibit an increased resistance to reduce or inhibitfluid flow therethrough, the treatment means being connected in serieswith the fluid displacement means; shut-01f valves between the treatmentsection and the inlet and outlet and operable to isolate the treatmentsection; and a by-pass connected between the inlet and the outlet inparallel with the treatment section, the by-pass being permanently openduring operation of the apparatus; wherein the fluid displacement meanshas a rate of fluid displacement greater than the rate of fluid flowthrough the inlet under normal operating conditions of the apparatus sothat under said conditions the fluid displacement means draws fluid fromboth the by-pass and the inlet and wherein fluid passes from the inletto the outlet along the by-pass upon an increase of said resistanceabove a pre-determined value.

7. Apparatus for the treatment of a fluid flow comprising a fluid inlet;a fluid outlet; a fluid treatment section connected between the inletand the outlet and comprising fluid displacement means and fluidtreatment means having a normal resistance to fluid flow therethroughbut being liable to exhibit an increased resistance to reduce or inhibitfluid flow therethrough, the treatment means being connected in serieswith the fluid displacement means; and a valveless by-pass connected inparallel with the treatment section between the inlet and the outlet sothat the by-pass is permanently open during operation of the apparatus;wherein the fluid displacement means has a rate of fluid displacementgreater than the rate of fluid flow through the inlet under normaloperating conditions of the apparatus so that under said conditions thefluid displacement means draws fluid from both the by-pass and the inletand wherein fluid passes from the inlet to the outlet along the by-passupon an increase of said resistance above a pre-determined value.

8. Apparatus for the treatment of a fluid flow comprising a fluid inlet;a fluid outlet; a fluid treatment section connected between the inletand the outlet and comprising a fan and fluid treatment means having anormal resistace to fluid flow therethrough but being liable to exhibitan increased resistance to reduce or inhibit fluid flow therethrough,the treatment means being connected in series with the fan; and aby-pass connected between the inlet and the outlet in parallel with thetreatment section, the by-pass being permanently open during operationof the apparatus; wherein the fan has a rate of fluid displace mentgreater than the rate of fluid flow through the inlet under normaloperating conditions of the apparatus so that under said conditions thefan draws fluid from both the by-pass and the inlet and wherein fluidpasses from the inlet to the outlet along the by-pass upon an increaseof said resistance above a predetermined value.

References Cited in the file of this patent UNITED STATES PATENTS2,536,663 Schaer Jan. 2, 1951

